EBV is associated with a number of B cell and epithelial cell malignancies, including B-cell lymphoproliferative disease in immunosuppressed patients, Burkitt lymphomas, and nasopharyngeal carcinomas. We hypothesize that new approaches that specifically target EBV-infected cells for destruction will be useful for the treatment of EBV-positive malignancies. In this project, we propose to develop three different EBVbased approaches for the treatment of EBV-induced tumors, capitalizing upon our extensive knowledge of EBV gene regulation and viral pathogenesis. In aim 1, we will inhibit the latent viral protein, EBNA1, to identify viral contributions that sustain EBV-associated lymphomas and thereby identify targets for specific anti-viral, anti-tumor therapies. In aim 2, we will examine the role of sirtuins (type III HDACs) in regulating viral latency, and determine if strategies for lytic-induction (whereby the virus is switched from the latent to lytic form of infection in tumor cells) can be enhanced using agents which regulate sirtuin activity, or agents that block the function of a negative regulator of lytic gene transcription (ZEB-1). In aim 3, based upon our exciting finding that HSP-90 is required for expression of an essential viral transforming protein, we will examine the importance of HSP-90 in viral pathogenesis and determine if newly developed HSP-90 inhibitors can be used specifically to kill EBV-transformed B cells in vitro and inhibit the growth of lymphoproliferative lesions in SCID mouse models. We will also determine if HSP-90 inhibitors can be used to block the lytic form of viral replication. Our proposed studies will lead to the identification of new targets for developing anti-EBV therapies and may lead to the identification of known drugs rationally chosen by EBV-based strategies for treating EBV-associated malignancies.